Estrella Resources Limited (ASX: ESR) has intersected 22.85m of nickel-copper-iron sulphides containing several zones of massive to globular sulphide mineralisation at the company’s 100% owned Carr Boyd Nickel-Copper Project, located ~80km north of Kalgoorlie in Western Australia.
Hole CBDD054B was designed to be drilled into the open area above CBDD030 and CBDD033 which both intersected significant massive to globular nickel-copper-iron sulphides. CBDD054B intersected the basal contact between and above these two holes.
The mineralisation intersected shows the repeated formation and disturbance of massive nickel-copper sulphides. Globular sulphides are the result of disturbing a layer of massive sulphides with pulses within the magma feeder. The top of the massive sulphide gets dislodged and deposited some way down the flow direction. As the dislodged sulphides begin to settle again, they tend to join together into larger “globules” and eventually reform massive sulphides if velocity of the magma flow permits.
Hole CBDD049C was completed by the DDSR diamond rig at the same time as CBDD054B made the intersection. The core shows 2.5m of breccia matrix and globular sulphide at 373m before entering a dolerite dyke for the remainder of the hole which was terminated at 415m. Due to the dolerite dyke exhuming the footwall, no accurate estimation of potential massive sulphide formation can be made at this location although given other holes in the vicinity, massive sulphide here is unlikely.
Managing Director, Chris Daws, said the closer spaced drilling in Phase 3 is beginning to bear fruit as the details are studied.
Our sustained drilling efforts at Carr Boyd continue to provide strong evidence that a substantial body of nickel-copper-iron sulphides can be located within our 100% owned Carr Boyd project area,” Mr Daws said.
“The company has never been in a stronger position than it is today to unlock Carr Boyd’s potential. I look forward in reporting assays on the numerous massive sulphide intersections we have made to date at T5 when they arrive and further drilling results as we continue at full stride 24/7 at the project.”
Mr Daws said the massive sulphide formation in the area appears to be roughly perpendicular to the flow direction.
“This makes sense when one visualises the comparison of the effect of waves causing ripples in the sand at the edge of a lake. The ripples are perpendicular to the direction of water movement. The mechanical movement of massive sulphides at T5 means that the immediate potential for further massive nickel-copper-iron sulphides should lie up plunge to the north and down plunge to the south (towards the Carr Boyd Rocks Mine).
“However, just as there are many ripples on a lake edge, so too is there the potential for other parallel, south plunging massive sulphide deposits which should be found by following the direction of flow.”
The sulphides are extremely dense when compared to the magma within the flow and will not stay suspended for long once any turbidity subsides. As such the down-dip (down-flow) location is an excellent massive sulphide exploration target. The precise location of “downstream” sulphide settling is currently unknown as very limited deep drilling has ever been undertaken within or along the T5 pyroxenite.
Moreover, sulphide assimilation mapped at Carr Boyd and study of the geological textures at T5, combined with mapping and 3D interpretation of the Carr Boyd Igneous Complex, leads the company to believe that the entire T5 Pyroxenite surface is in the correct orientation to be a sulphide trap with respect to the flow direction and resulting flow dynamics.
The remaining 50% of Phase 3 will concentrate on the massive sulphide extensions of the Upper T5 Conductor, both up and down plunge. This will give time for assays to arrive and for the results of the seismic survey to be interpreted. Drilling will utilise the RC capability of one of the current multipurpose rigs onsite to drill pre-collars with multiple diamond tails which will provide a cost saving and increase the speed of the targeted drilling campaign.
The drilling in Phase 4 will be predominantly RC, targeting the T5 Pyroxenite directly above the current mineralisation, south past the Carr Boyd Rocks Mine and more than 3.5km north along what the Company believes to be a highly prospective orientation of the T5 pyroxenite basal contact.
As this phase will be mainly RC drilling the Company hopes to quickly understand the prospectivity of this area and conduct deeper drilling upon additional mineralisation being located. It is estimated that this will be completed before the end of the calendar year.
Any intersections will be followed up with diamond tails and DHTEM, utilising the detailed knowledge of the mineralisation model learned in Phase 3 to vector in on any additional massive sulphides that the Company believes should be found on the T5 Contact.
Targeting during Phase 4 will also be supported by modelling of the basal contact resulting from the seismic survey with additional Fixed Loop Transient Electromagentics (FLTEM). The FLTEM should be more effective once the location of the contact is known and surface loops can be placed in optimal positions to test the contact.
Drilling early next year will build on Phases 3 and 4. It will have a more regional component to follow up nickel-copper sulphide intersections at Tregurtha, POH, Drinkwater and Schmidt.
Targeting in Phase 5 will utilize the seismic interpretation and FLTEM. It will also draw upon a collaborative project that will begin in August between the CSIRO and Estrella, specifically targeting geochemical vectors developed by the CSIRO to locate nickel-copper sulphides under cover.